Various kinds of sesame lignan are found in sesame seeds and it is known that they usually contain not only sesamin in about 0.1-0.5 wt % but also sesamol, sesamolin, sesaminol and the like. Unrefined sesame oil expressed from sesame seeds contain about 0.5-1.0 wt % of sesamin as a sesame lignan.
It is also known that when sesame seeds are treated with mineral acids such as sulfuric acid, activated clay, or the like, sesamin components are formed, including not only sesamin but also episesamin that is an optically converted product of sesamin and which inherently is not present in sesame seeds (non-patent reference 1 and non-patent reference 2). Such sesame lignans mainly comprising sesamin components are known to have various physiological activities including, for example, the action of inhibiting Δ5-unsaturation enzymes, anti-oxidizing action against lipids, antihypertensive action, the action of improving hepatic functions, the action of scavenging active oxygen, cholesterol lowering action, and the action of preventing sickness from drinking and, hence, they are expected to prove useful as health food.
As a method by which products containing sesamin components at high concentrations can be separated from sesame seeds, it has been proposed to press sesame seeds, subject the pressed seeds to extraction with an organic solvent, and perform molecular distillation on the extract. Specific examples include: (1) distilling sesame oil with steam under reduced pressure and subjecting the distillate to molecular distillation (see patent reference 1); (2) distilling sesame oil with steam under reduced pressure, performing esterification reaction and/or ester exchange reaction on the distillate, and subjecting the reaction product to molecular distillation (see patent reference 2); (3) distilling sesame oil with steam, mixing the distillate with an aqueous solvent, and performing crystallization in the mixed system in the presence of an alkali (see patent reference 3); (4) distilling sesame oil with steam under reduced pressure, mixing the distillate with an aqueous ethanol solution containing at least 40 wt % of ethanol, separating the solution fraction from the mixed system, and adding an alkali to the solution fraction for crystallization (see patent reference 3); (5) distilling sesame oil with steam under reduced pressure, mixing the distillate with an aqueous ethanol solution containing at least 40 wt % of ethanol, separating the solution fraction from the mixed system, performing adsorption treatment on the separated solution fraction with an adsorbent, and performing desorption/elution from the adsorbent (see patent reference 4); and the like. It has also been disclosed that the molecular distillation, crystallization or desorption/elution that are performed in (1)-(5) above may even be followed by recrystallization treatment to increase the concentrations of sesamin components (wherein the term “sesamin components” is defined to comprise sesamin, episesamin and sesamolin) (patent references 1-2).
Recent studies on the differences between the physiological activities of sesamin and episesamin have revealed the superiority of episesamin over sesamin, as exemplified by higher transfer into organs, enhanced gene expression of β-oxidation enzymes in the liver, and marked enhancement of enzymatic activity (non-patent reference 3 and non-patent reference 4).    [Patent reference 1] the official gazette of JP 7-25764 B    [Patent reference 2] the official gazette of JP 2003-183172 A    [Patent reference 3] the official gazette of JP 10-7676 A    [Patent reference 4] the official gazette of JP 6-89353 B    [Non-patent reference 1] Namiki et al., “Goma—Sono Kagaku to Kinousei (Sesame—Its Science and Functions)”, Maruzen Planet Co., Ltd. (1998)    [Non-patent reference 2] Fukuda, Y. et al., J. Am. Oil Chem. Soc., 63, 1027-1031 (1986)    [Non-patent reference 3] Sawada, R. et al., Lipids, 34, 633 (1999)    [Non-patent reference 4] Kushiro, M. et al., J. Nutr. Biochem., 13, 289-295 (2002)